Method of oxidation stability testing of lubricants

FIELD: measuring technique.

SUBSTANCE: method comprises testing two samples of the lubricant of the same mass, the first sample being tested without catalyzer and the second sample being tested in the presence of catalyzer, determining transparency coefficient by means of photometric measurements, plotting time dependences of the transparency coefficient, and determining oxidation stability of the lubricant from the equation presented.

EFFECT: enhanced precision.

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The invention relates to the testing of lubricating oils and can be used in laboratories to study the impact of metals on the oxidation processes taking place in lubricants, for determining the catalytic activity.

There is a method of determining oxidative stability of lubricants (RF patent No. 2057326, IPC G01N 25/02, publ. 27.03.96), which consists in heating oil in the presence of air stirring, and the determination of the valuation parameters of the oxidation process. The test is subjected to two tests of the lubricant. Preliminary photometry determine the optical density of samples of the original lubricant, then heated simultaneously with the mixing of the first sample to a certain temperature, maintain it at a predetermined temperature during the time interval, at the end of which determine the optical density, and then increase the temperature to the selected step, maintain the sample at each temperature value in the interval, at the end of which determine the optical density and build the graphical dependence of the optical density from the temperature at the inflection point which determine the onset temperature of oxidation, then heated a second sample to a temperature above the onset temperature of oxidation, maintain it with shortcuts is bent temperature and determine the optical density in selected intervals of time, build graphical dependence of the ratio of optical density of the oxidized lubricant to the optical density of the original lubricant from the time of oxidation and the tangent of the angle of the line to the x-axis on the plot to the point and inflection lines determine the rate of formation of soluble oxidation products, and the tangent of the slope of the line is the rate of formation of insoluble oxidation products.

The closest in technical essence and the achieved result is a method for determining oxidative stability of lubricants (RF patent 2219530, IPC G01N 25/02, publ. 20.12.2003), namely, that the lubricant is heated in the presence of air, mix, photometrate and determine the parameters of the evaluation of the oxidation process. Experience a sample of the lubricant constant volume at the optimum temperature selected depending on the underlying fundamentals of the lubricant and group performance properties over time, characterizing the same degree of oxidation, and at equal intervals of time selected sample oxidized lubricant is determined by photometry absorption coefficient of the light flux oxidized lubricant, build the graphical dependence of the absorption coefficient of the light flux from the time of testing, extend the line based after the inflection point to the intersection with the x-axis and the abscissa of this point determines the start time of the formation of insoluble impurities, the inflection point dependencies define the start time of coagulation of insoluble impurities, and the limiting value of the absorption coefficient of the light flux determine the resource efficiency of the lubricant.

A disadvantage of the known technical solutions is the low information content of the indicators of the processes of oxidation time and the resulting oxidation products.

The basis of the invention is the determination of oxidative stability of lubricants in the presence of catalysts influencing the increase in the information content and accuracy evaluation of oxidative stability of lubricants by obtaining additional information about the manifestation of the beginning of the catalytic activity of metals and quantitative assessment of changes in oxidative stability against the action of the catalyst, i.e. the energy of the absorbed test environment, which are the products of oxidation and destruction of the basic fundamentals and additives.

The problem is solved in that in the method for determining oxidative stability of lubricants, including the heated lubricant m is material in the presence of air, mixing, sampling oxidized lubricant, photomatrixovina and determination of the parameters of the oxidation process in the graphical dependencies, according to the invention have two samples separately lubricant constant mass, without first catalyst, the second catalyst at the same temperature for a set time, and at equal intervals of time selected sample oxidized lubricant is determined by photometry transmittance of the light flux To aCRwithout catalyst and with it, build the graphical dependence of the transmittance change of the luminous flux of oxidized lubricant from the test time and time and value define the beginning of the catalytic activity of the catalyst and thermal-oxidative stability of lubricants is determined by the ratio of the catalytic activity of metals ToKDaccording to the expression:

ToKD=S/Sto,

where S is the area of the curve of the transmittance of the light flux from the time of the test lubricant without catalyst, mm2,

Sto- area curve of the transmittance of the light flux from the time of the test lubricant with catalyst, mm2.

Comparative analysis of the prototype and savla the constituent method showed that the latter has the following distinctive features.

Determination of the coefficient of the catalytic activity on oxidative stabilityKDas the ratio of the areas of the curves dependency test lubricant [CCR=ƒ(t)], characterizing thermal energy absorbed, respectively, when tested lubricant without catalyst and with him, for an accepted period of time, allows us to estimate the activity of the catalytic activity of metals.

The construction of the graphical dependency of the transmittance change of the luminous flux of the test lubricant from the time of testing allows you to visualize the kinetics of oxidation and to determine the time parameters characterizing catalytic effect on thermal-oxidative stability of lubricants: the beginning of the catalytic activity of the catalyst; area curves dependency of the transmittance of the light flux from the time of the test lubricant with catalysts and without them; the ratio of the catalytic activity on oxidative stability. All these indicators are aimed at solving the task at hand - improving the accuracy and reliability of the oxidative stability of lubricants by obtaining additional information about proyavlena the beginning of the catalytic activity of metals and the ratio of the catalytic activity on oxidative stability of lubricants.

Figure 1 shows the dependence of the transmittance of the light flux from the time-tested mineral oil free of catalysts and with them; figure 2 - dependence of the transmittance of the light flux from the test time partially synthetic oils; figure 3 - dependence of the transmittance of the light flux from the time tested synthetic oil.

The method for determining oxidative stability of lubricants is as follows.

The glass beaker with the test oil without catalyst mass 100 g is installed in a cylindrical furnace installation to determine oxidative stability, is heated to the optimal temperature, for example 180°C, with an accuracy of ±2°and mixed with air by a mechanical device. In the process of testing every 2 hours take a sample of lubricant, photometrate and determine thermal-oxidative stability of the transmittance of the light flux from the expression KCR=P/300, where N is the index of the photometer when the photometry of the test sample lubricant, MCA; 300 - index of the photometer in the absence of oil in the photometric cuvette, MCA. In parallel, the same make with the same oil with the catalyst as the metal samples. To study the effect of base metals and base what you lubricant were selected motor oil mineral (M-6 C/10-In), partially synthetic (Sibi Motor 10W-40 SJ/CD) and synthetic (Mannol 5W-40 SJ/CF) basis. As metal samples selected Steel 3 (GOST 380-71), copper M1 (GOST 495-77) and steel SHKH15 (GOST 801-60), which is a disk with a diameter of 40 mm, thickness 2 mm of the sample Surface was polished, and before the test was obezzhirivaete petrol a-80.

The results build the graphical dependence of the transmittance of the light flux oxidized lubricant from the test time [ToCR=ƒ(t)]. These curves have a point of inflection O1About2About3that characterize the beginning of the catalytic activity of metals on the oxidation of oils. The slower metals contribute to the oxidation of oils and the transmittance of the light flux is smaller, the better thermo-oxidative stability have oil. The coordinates of the points O1About2About3indicate the start of the action of the catalyst, after which the catalytic activity of metals reduces thermal-oxidative stability.

Evaluation of the effect of metal catalysts on the oxidation mechanism of lubricants produced by the coefficient characterizing the catalytic effect on thermal-oxidative stabilityKDand defined by the ratio of the areas of the curve according To thePR =ƒ(t) a lubricant without catalyst and with him. Review the graphics according To theCR=ƒ(t) determined that a more active catalytic effect manifests copper. To quantify the catalytic action of metals on oxidation processes in lubricants, we offer a ratio of the catalytic activity, which is determined from the expression:

ToKD=S/Sto,

where S is the area of the curve of the transmittance of the light flux from the time of the test lubricant without catalyst, mm2,

Sto- area curve of the transmittance of the light flux from the time of the test lubricant with catalyst, mm2.

A characteristic feature of the obtained dependences is that the effect of catalysts on the oxidation is determined by the change To aKD. The more ItKDthe greater the influence of the catalyst on the oxidation processes. As a result of research on mineral oil (figure 1) found that the change in oxidative stability depends on the basic fundamentals of the oil and the type of metal catalyst, the effect of which is determined by finding the ratio of the catalytic activity on oxidative stability.

The results of the Ana is iza mineral (1), partially synthetic (figure 2) and synthetic (figure 3) lubricants are summarized in the table on the proposed indicators characterizing the catalytic action of metals on thermal-oxidative stability of lubricants. These indicators include: the start time of the catalytic activity of the catalyst; area curves dependency of the transmittance of the light flux from the time of the test lubricant with catalysts and without them; the ratio of the catalytic activity on oxidative stability.

Thermal-oxidative stability of mineral oils (figure 1) is reduced when tested in the presence of catalysts, and the manifestation of the catalytic activity of steel ST.3 comes after 17 hours of testing, and steel SHKH15 and copper after two hours of testing, and the intensity of oxidative processes, equal to 11.5 hours of testing, and then branches dependencies differ. The greatest influence on the oxidative processes has copper as the start time of the catalytic activity of metals is 11.5 h, the area of the curve of the transmittance of the light flux from the time - 12,148 and the ratio of the catalytic activity is greatest - 1,168.

Thermal-oxidative stability of partially synthetic oils (figure 2) increases in the presence of all islebe what's catalysts. A characteristic feature of the obtained dependences is that up to five hours of testing, the metals have the same effect on oxidative processes, and then testing time they split into two branches: one branch is characterized by the influence of the steel ST.3 and copper, and the second steel SHKH15, and from the first branch after 13 hours of testing, there is a branch of characterizing the influence of steel ST.3 on oxidative processes, which provides a more intense effect on the oxidation. Compared with mineral oil of the investigated catalysts to a lesser extent influence the oxidation of partially synthetic oils and are oxidation inhibitors. The best inhibitor is copper, because the start time of the catalytic activity of steel ST.3 and copper is 2.0 h, and SH-15 steel - 5 h, the area of the curve of the transmittance of the light flux from the time the highest - 8,586 and the ratio of the catalytic activity is the lowest - 0,894.

The effect of catalysts on the oxidation of synthetic oils, (3) slightly and appears at the beginning of the test and is one according to 6.6 hours of testing, and then it splits into two branches, one evaluated the same effect steel ST.3 and copper, and other steel SHKH15. More active catalytic action takes place on sizenumericgloballog stability of the oil, copper and steel 3, as the start time of the catalytic activity amounted to 6.6 h, the area of the curve of the transmittance of the light flux - 17,659 and 17,68, the ratio of the catalytic activity - and at 1,046 1,045.

Thus, the proposed method can enhance the usefulness and accuracy of the evaluation of oxidative stability of lubricants.

Table
IndicesExample 1Example 2Example 3
the mineral oil M-6C/10-Inmotor oil semi synthetic Sibi Motor 10W-40 SJ/CDsynthetic motor oil Mannol 5W-40 SJ/CF
without catalystscatalystswithout catalystscatalystswithout catalystscatalysts
+Cu+ steel SHKH15+ St3+Cu+ steel SHKH15+ St3+Cu+ steel SHKH15+ St3
The start time of the catalytic activity of the catalyst, h -11,516,217-2,052,0-6,611,86,6
The ratio of the catalytic activity on oxidative stability11,1681,0681,01510,8940,9490,9071at 1,0461,0261,045
Area curves dependency ratio oxidative stability from the time of the test oils, mm214,19512,14813,29513,9857,6778,5868,098,45918,47317,65918,01517,68
Note: the testing time for mineral and synthetic oils - 20 hours; partially synthetic - 13 h; temperature tests 180°

The method for determining oxidative stability of lubricants, including heating the lubricant in the presence of air, mixing, sampling oxidized lubricant, photomatrixovina, determination of the parameters of the oxidation process on the graphics according to different t is m, they are separately two samples of the lubricant constant mass, without first catalyst, the second catalyst at the same temperature for a set time, and at equal intervals of time selected sample oxidized lubricant is determined by photometry transmittance of the light flux without catalyst and with it, build the graphical dependence of the transmittance change of the luminous flux of oxidized lubricant from the test time and time and the value of the specified coefficient determine the beginning of the catalytic action of the catalyst and thermal-oxidative stability of lubricants is determined by the ratio of the catalytic activity of metals ToKDthe expression

ToKD=S/Sto,

where S is the area bounded by the curve of the dependence of the transmittance of the light flux from the time of the test lubricant without catalyst, mm2,

Sto- the area bounded by the curve of the dependence of the transmittance of the light flux from the time of the test lubricant with catalyst, mm2.



 

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